Foreign murderers and rapists have been free to prey on the British public for a year because of yet another data loss scandal.

DNA samples for up to 4,000 suspects, wanted for a range of serious crimes, were circulated throughout Europe by the Dutch authorities in January 2007.

In Britain, they were sent to the Attorney General's office, which passed them to the Crown Prosecution Service.

But the CPS mislaid the disks for more than a year. Staff only found them again last month. So far they have worked their way through half the list, and have already identified 15 matches. Of those, 11 had committed offences including serious assaults.

It is not known how many have since been caught.

It is understood ministers were first told of the significance of the matches up to 10 days ago but did not make it public because police are still investigating.

It is not known when the Home Secretary was alerted or the Director of Public Prosecutions Sir Ken MacDonald.

Last night a CPS spokesman said: "This is not a data security issue as this information was always in the possession of the CPS." But Shadow Home Secretary David Davis said: "We do not know if the Home Secretary or the Prime Minister knows about this.

"Yet again we have a disastrous case of data loss that has an implication for public safety." The disks were lost around the time the Home Office admitted that 27,500 criminal convictions committed by Britons overseas had not been entered on the Police National Computer.

Shadow Police Minister David Ruffley said: "Government incompetence has put the safety of our citizens at risk yet again."